The International Telegraph and Telephone Consultative Committee (CCITT) is a standards organization who, inter alia, publishes recommendations for data communication over telephone networks. The 1984 Series V Recommendations include recommendations for wideband modems. Section 3 of this document is titled "Recommendation V.35--Data Transmission at 48 Kilobits per second Using 60-108 Khz Group Band Circuits", which is hereby expressly incorporated by reference. The appendix to this letters patent (identical to Appendix II of the CCITT V.35--1984 recommendation) describes the electrical characteristics for the balanced, double-current interchange circuits which are used with this recommendation. The Recommendation V.35 uses differential signals (two signals), which give a much higher signal-to-noise ratio than signals referenced to ground.
The present invention allows an efficient conversion from transistor-transistor logic (TTL) signals to the V.35 electrical interface, and vice versa.